1099 Build A Binary Search Tree （30 分）

A Binary Search Tree (BST) is recursively defined as a binary tree which has the following properties:

• The left subtree of a node contains only nodes with keys less than the node's key.
• The right subtree of a node contains only nodes with keys greater than or equal to the node's key.
• Both the left and right subtrees must also be binary search trees.

Given the structure of a binary tree and a sequence of distinct integer keys, there is only one way to fill these keys into the tree so that the resulting tree satisfies the definition of a BST. You are supposed to output the level order traversal sequence of that tree. The sample is illustrated by Figure 1 and 2.

Input Specification:

Each input file contains one test case. For each case, the first line gives a positive integer N (≤100) which is the total number of nodes in the tree. The next N lines each contains the left and the right children of a node in the format left_index right_index, provided that the nodes are numbered from 0 to N−1, and 0 is always the root. If one child is missing, then −1 will represent the NULL child pointer. Finally N distinct integer keys are given in the last line.

Output Specification:

For each test case, print in one line the level order traversal sequence of that tree. All the numbers must be separated by a space, with no extra space at the end of the line.

Sample Input:

9
1 6
2 3
-1 -1
-1 4
5 -1
-1 -1
7 -1
-1 8
-1 -1
73 45 11 58 82 25 67 38 42

Sample Output:

58 25 82 11 38 67 45 73 42

 

#include<bits/stdc++.h>
using namespace std;
struct node
{
    int data;
    int left,right;
}root[105];
int d[105],num=0;
void inorder(int x)
{
    if(root[x].left!=-1)
        inorder(root[x].left);
    root[x].data = d[num++];
    if(root[x].right!=-1)
        inorder(root[x].right);
}

int main()
{
    int n;
    cin>>n;
    for(int i=0;i<n;i++)
    {
        cin>>root[i].left>>root[i].right;
    }
    for(int i=0;i<n;i++)
        cin>>d[i];
    sort(d,d+n);
    inorder(0);
    queue<node>q;
    q.push(root[0]);
    vector<int>v;
    while(!q.empty())
    {
        node t = q.front();
        q.pop();
        v.push_back(t.data);
        if(t.left!=-1)
            q.push(root[t.left]);
        if(t.right!=-1)
            q.push(root[t.right]);
    }
    for(int i=0;i<v.size()-1;i++)
        cout<<v[i]<<" ";
    cout<<v[v.size()-1];
}